import java.util.ArrayList;
import java.util.LinkedList;
import java.util.List;
import java.util.Queue;

/**
 * Created with IntelliJ IDEA.
 * Description:
 * User: WHY
 * Date: 2023-01-07
 * Time: 23:58
 */ public class BinaryTree {

    static class TreeNode {
        public char val;
        public TreeNode left;//左孩子的引用
        public TreeNode right;//右孩子的引用

        public TreeNode(char val) {
            this.val = val;
        }
    }

    public TreeNode root;


    /**
     * 创建一棵二叉树 返回这棵树的根节点
     *
     * @return
     */
    public TreeNode createTree() {
        TreeNode A = new TreeNode('A');
        TreeNode B = new TreeNode('B');
        TreeNode C = new TreeNode('C');
        TreeNode D = new TreeNode('D');
        TreeNode E = new TreeNode('E');
        TreeNode F = new TreeNode('F');
        TreeNode G = new TreeNode('G');
        TreeNode H = new TreeNode('H');
        A.left = B;
        B.left = D;
        B.right = E;
        C.left = F;
        C.right = G;
        E.right = H;
        this.root = A;
        return root;


    }

    // 前序遍历
    public void preOrder(TreeNode root) {
        if (root == null) {
            return;
        }
        System.out.println(root.val + "");
        preOrder(root.left);
        preOrder(root.right);
    }

    // 中序遍历
    void inOrder(TreeNode root) {
        if (root == null) {
            return;
        }
        inOrder(root.left);
        System.out.println(root.val + "");
        inOrder(root.right);

    }

    // 后序遍历
    void postOrder(TreeNode root) {
        if (root == null) {
            return;
        }
        postOrder(root.left);
        System.out.println(root.val + "");
        postOrder(root.right);


    }

    public static int nodeSize;

    /**
     * 获取树中节点的个数：遍历思路
     */
    public int NodeSize;//成员变量

    void size(TreeNode root) {
        if (root == null) {
            return;

        }
        NodeSize++;
        size(root.left);
        size(root.right);
    }

    /**
     * 获取节点的个数：子问题的思路
     *
     * @param root
     * @return
     */
    int size2(TreeNode root) {
        if (root == null) {
            return -1;
        }
        int leftSize = size2(root.left);
        int rightSize = size2(root.right);
        return leftSize + rightSize + 1;

    }


    /*
     获取叶子节点的个数：遍历思路
     */
    public static int leafSize = 0;//静态成员变量

    void getLeafNodeCount1(TreeNode root) {
        if (root == null) {
            return;
        }
        if (root.left == null && root.right == null) {
            leafSize++;
        }
        getLeafNodeCount1(root.left);
        getLeafNodeCount1(root.right);

    }

    /*
     获取叶子节点的个数：子问题
     */
    int getLeafNodeCount2(TreeNode root) {
        if (root == null) {
            return -1;
        }
        if (root.left == null && root.right == null) {
            return 1;
        }
        int leftSize = getLeafNodeCount2(root.left);
        int rightSize = getLeafNodeCount2(root.right);
        return leftSize + rightSize;

    }

    /*
    获取第K层节点的个数
     */
    int getKLevelNodeCount(TreeNode root, int k) {
        if (root == null) {
            return -1;
        }
        if (k == 1) {
            return 1;
        }
        int leftSize = getKLevelNodeCount(root.left, k - 1);
        int rightSize = getKLevelNodeCount(root.right, k - 1);
        return leftSize + rightSize;


    }

    /*
     获取二叉树的高度
     时间复杂度：O(N)
     */
    int getHeight(TreeNode root) {
        if (root == null) {
            return -1;
        }
        int leftHeight = getHeight(root.left);
        int rightHeight = getHeight(root.right);
        return (leftHeight > rightHeight) ? leftHeight + 1 : rightHeight + 1;
    }


    // 检测值为value的元素是否存在
    TreeNode find(TreeNode root, char val) {
        if (root == null) {
            return null;
        }
        if (root.val == val) {
            return root;
        }
        TreeNode leftNode = find(root.left, val);

        if (leftNode != null) {
            return leftNode;
        }
        TreeNode rightNode = find(root.right, val);
        if (rightNode != null) {
            return rightNode;
        }

        return null;
    }

    //层序遍历
    void levelOrder(TreeNode root) {
        if (root == null) {
            return;
        }
        Queue<TreeNode> queue = new LinkedList<>();
        queue.offer(root);
        while (!queue.isEmpty()) {
            TreeNode cur = queue.poll();
            System.out.println(cur.val + "");
            if (cur.left != null) {
                queue.offer(cur.left);
            }
            if (cur.right != null) {
                queue.offer(cur.right);
            }


        }

    }

    public List<List<Integer>> levelOrder1(TreeNode root) {//层序遍历
        if (root == null) {
            return null;
        }
        List<List<Integer>> list = new ArrayList<>();
        Queue<TreeNode> queue = new LinkedList<>();
        queue.offer(root);
        while (!queue.isEmpty()) {
            int size = queue.size();
            List<Integer> ret = new ArrayList<>();
            while (size != 0) {
                TreeNode cur = queue.poll();
                System.out.println(cur.val + "");
                ret.add(cur.val);
                size--;
                if (cur.left != null) {
                    queue.offer(cur.left);
                }
                if (cur.right != null) {
                    queue.offer(cur.right);
                }

            }
            list.add(ret);

        }
        return list;

    }


    // 判断一棵树是不是完全二叉树
    boolean isCompleteTree(TreeNode root) {
        if (root == null) {
            return true;
        }
        Queue<TreeNode> queue = new LinkedList<>();
        queue.offer(root);
        while (!queue.isEmpty()) {
            TreeNode cur = queue.poll();
            if (cur != null) {
                queue.offer(cur.left);
                queue.offer(cur.right);
            } else {
                break;
            }
        }
        //判断，到这一步的时候，站不为空，那么就是cur==null。所以就要开始判断弹出的每一个元素是不是null
            while (!queue.isEmpty()) {
                TreeNode tmp = queue.poll();
                if (tmp != null) {
                    return false;
                }
            }
            return true;

        }
    }







